The specific aim of this proposal is to upgrade our single-wavelength optical imaging scanner for small animals. The upgrade will permit the scanner to operate at 4 wavelengths. This will provide new capabilities to enhance current research by permitting a variety of optical molecular probes to be imaged simultaneously. Currently we have a first generation of the eXplore Optix(tm) scanner, which only operates at 750 nm and is limited to imaging solely Cy7-based optical probes. The proposed upgrade will incorporate 3 additional wavelengths, namely the 470 nm, 650 nm, and 780 nm modules, which will permit time domain fluorescence imaging of GFP, Cy5, and Cy7.5 respectively. The ability to simultaneously measure two or more optical probes during the same experiment will permit the simultaneous measurement of two or more physiologic and/or molecular processes. Our small animal imaging laboratory also has PET and CT imaging devices, but the upgraded explore Optix(tm) scanner will be unique in its ability to control for permeability and/or flow at the same time that we are measuring biochemistry. The UCSD Molecular Imaging Program has many investigators in cancer, molecular biology, chemistry, pharmacology, and radiology. This proposal lists 12 projects that will benefit from the upgraded imager. The simultaneous measurement of multiple processes will provide a tool to answer a question that is central to most molecular image experiments: if a target tissue exhibits increased uptake, is the higher uptake due to increased delivery (blood flow or ligand permeability) or an increase in the affinity or density of the molecular target? At present, these measurements must be conducted in separate animals, which lowers the statistical power to quantify differences. Relevance: Molecular imaging of small animals will play a vital role in the development of imaging protocols for diagnosis and therapy. Properly designed optical imaging experiments permit the simultaneous measurement of multiple molecular processes. By simultaneously detecting optical molecular probes, the instrument can gather greater amounts of information from a single experiment. Consequently, the upgrade of our optical imager to multi-wavelength capability will promote the development towards long- term human applications of molecular imaging. Our long-term objective is to translate optical molecular probes from rodent disease models to the diagnosis and management of human disease. This upgrade will accelerate the path from bench to bedside. [unreadable] [unreadable] [unreadable]